This invention relates to a feeding system for feeding crop material to a cutterhead, for example in a forage harvester, and more particularly to an articulation and control arrangement for a yieldably floating conveyor forming part of such a system.
Forage harvesters for removing material from a field, reducing its size or cut length and delivering it to a trailer or other collector are well known. In a very common type of machine, a feeding system transfers harvested crop material from a harvesting unit to a cylinder or reel-type cutterhead, the axes of the feed rolls or rotating members of the conveyor being parallel to the cutterhead axis and feeding the material to the cutterhead in a generally radial direction. Generally the cutterhead and its feeding system are housed between parallel generally upright opposite side walls and, typically, the feeding system consists of two opposed conveyor assemblies, one of which (usually the lower) is fixed in relation to the cutterhead while the other is free to float to increase feed opening to accommodate variations in flow of crop material but restrained by some resilient means so as to maintain pressure on the mat of material being fed and to ensure positive and efficient feeding. For convenience in this discussion it will be assumed that the upper conveyor is the yieldable one.
Typically, such a conveyor consists of generally cylindrical side-by-side rolls with their cylindrical surfaces treated (for example, provided with toothed axially extending ribs) to positively convey material, although an endless belt-type conveyor may be used in which an apron is drivingly supported on a plurality of rolls. The tendency of a yieldably floating upper conveyor assembly to cock or tilt due to lateral unevenness in the mat of crop material has long been a problem. Where cocking must be tolerated, extra clearances between the ends of the rolls and the side walls must be provided, possibly resulting in wrapping of the rolls and shafts with crop material, or loss of control of the mat being fed. Wear rates of drive components and bearings may also be increased. Various attempts have been made to provide support assemblies for the upper conveyor resistant to cocking and able to maintain roll alignment. These have included tieing or interconnecting opposite sides of the conveyor assembly adjacent the cutterhead, for example with a transverse shaft, journaled in support arms carrying the rolls and fitted with pinions at each end for engaging a mating rack attached to a side wall or frame. In another method, a torsionally stiff shaft journaled in the side walls or frame is connected to the opposite sides of the conveyor assembly by bell cranks and linkages. Such systems only partially solve the problem of cocking because they couple the opposite sides of the conveyor assembly only indirectly and their relative complexity introduces wear points and joint clearances, the slack of which must be taken up before uneven crop mat forces tending to lift one side of the conveyor can be transmitted from one side to the other so that both sides move in unison.
It is also known to provide a torsion member in an upper conveyor remote from the cutterhead but disposed externally and rearward of a forward feed roll and hence at a less mechanically advantageous point with regard to providing efficient torsional and bending resistance for a forward part of a conveyor subframe.
Another problem of forage harvesters has been to provide in the cutterhead feeding system a flexible, crop mat compressing upper conveyor assembly that is rapidly and smoothly responsive to changes in rate of crop flow and mat thickness and capable of applying uniform and steady pressure so that blockages and/or peak torque in the drive train are avoided. Many conveyor systems have relied on a slotted guide arrangement to provide part of the control of a floating conveyor movement with consequently somewhat unpredictable friction forces. Even in systems using only pivoted joints, the roll tensioning device has been applied indirectly by springs through rock shafts and linkages and with somewhat oblique direction of application of restraining force to a conveyor assembly subframe. Further, little attention has been given to optimizing the location of down stops for the upper conveyor assembly or provision of adjustment for them, or to provision of interlock means controlling relative movement between adjacent rolls of the upper conveyor assembly.